Amoebiasis is caused by the intestinal protozoan Entamoeba histolytica. Most infections are asymptomatic, but 10% can cause a spectrum of clinical syndromes ranging from asymptomatic to dysentery to liver and other organ abscesses. Transmission occurs through the fecal-oral route via contaminated food, water, or direct person-to-person contact. Diagnosis involves microscopic identification of trophozoites in stool or abscess samples and serologic detection of antibodies. Treatment depends on the infection site and involves luminal amoebicides for intestinal infection and tissue amoebicides like metronidazole for extra-intestinal infections such as liver abscesses.

2. 
Amoebiasis is an infection with the intestinal
protozoa Entamoeba histolytica.

About 90% of infections are asymptomatic

Remaining 10% produce a spectrum of clinical
syndromes

Ranging from -
asymptomatic to dysentery to abscesses of liver
or other organs

3. 
Entamoeba histolytica

Trophozoites
•
•
•
•
10 - 60 μm in D
Cytoplasm – # outer clear ectoplasm
# inner granular endoplasm
# food vacuoles with RBCs, leukocytes & tissue
debris
Motile by pseudopodial extensions
Nucleus with central karyosome, surrounded by delicate
membrane lined with chromatin granules

4. 
Entamoeba histolytica
 Precyst
Intermediate form
• Oval with blunt pseudopodia
• No food vacuoles
•
 Cysts
•
•
•
•
•
Spherical, 10 - 15 μm in D
Uninucleate, later bi- or quadri- nucleate
Thick chitinous wall
Glycogen mass – not in quadrinucleate
Chromidial or Chromatoid bars

5. World

worldwide in distribution

3rd most common parasitic death

India, China, Africa, South America

2-60% prevalence

100,000 deaths/yr

500 million infections

50 million cases
India

15% prevalence (3.6-47.4%)

variation according to sanitation

6. 
Source of infection is a case or carrier
-1∙5 X 107 cysts per day

Reservoir is only human – several years

Resistant to chlorine in normal conc.

Readily killed by freezing or heating(55 C)

8. 
All age groups affected

No gender or racial differences

Institutional, community living, MSM

Severe if children, old, pregnant, PEM

Develops antibodies in tissue invasion

9. 
Low socio-economic status

Poor sanitation, sewage contamination

Night soil for agriculture

Seasonal variation

10. 
1- 4 weeks

1- 4 weeks

Faeco -oral route
•
contaminated water and food
•
direct hand to mouth

Agency of flies, cockroaches, rats, etc.

Sexual contact via oro -rectal route

11. 
Most
common
type
of
amoebic
infection
is
asymptomatic cyst passage

Intestinal amoebiasis – abdominal cramps with mild
diarrhoea to colitis and dysentry

Extra-intestinal amoebiasis – Amoebic liver abcess,
rarely lungs, skin, genitalia and CNS are affected

Amoeboma – inflammatory and edematous reaction
around trophozoites

12. 
90% without symptoms

does not damage lumen

flask shaped ulcers superficial or deep

abd pain (tenesmus)

diarrhoea, dysentery, fever

peri-anal ulcers

<0.5%

severely ill with high fever

intestinal bleeding, perforation

paralytic ileus

CFR-40%

Uncommonly, a chronic form of amoebic colitis
can be confused with inflammatory bowel disease

13. 
Pseudotumoral lesion

Necrosis, edema and inflammatory thickening of mucosa
and submucosa of intestinal wall

1% of cases

palpable mass with trophozoites

Always coexists with ulceration

Single, rarely multiple in different parts of colon, on skin at site
of ALA aspiration

14. Macroscopy
Character
Amoebic dysentry
Bacillary dysentry
Number
6-8 motions per day
> 10 motions per day
Amount
Copious
Small
Odour
Offensive
Odourless
Colour
Dark red
Bright red
Acidic
Alkaline
Non-adherent
Adherent
Reaction
Consistency

15. Microscopy
Character
Amoebic dysentry
Bacillary dysentry
In clumps
Discrete or in Rouleaux
Pus cells
Few
Numerous
Macrophages
Few
Numerous, many have
RBCs and may mimic EH
Eosinophils
Present
Scarce
Charcot-Leyden crystals
Present
Absent
Pyknotic bodies
Present
Absent
Ghost cells
Absent
Present
Parasites
Trophozoites of EH
Absent
Bacteria
Many motile bacteria
Few or Absent
RBCs

16. 
Most common extra-intestinal presentation

The parasite reaches liver via portal system

Occurs within 5 mths of dysentery in 95% of cases

But concomitant active diarrhea is seen in less than a third of cases

Pain and point tenderness over right hypochondrium and fever

Jaundice rare, pleural effusion is common

Older pt. from endemic areas usually have chronic disease

Right lobe is commonly affected, abscess of left lobe is more dangerous
due to its proximity to heart –> rupture –> pericardial effusion

Necrotic cavitary lesion filled with cellular debris and parasite
trophozoites – Anchovy sauce pus

17. 
Rupture is the most dreaded complication

It may spread to pleura, lungs, peritoneum, pericardium or open
outside through the anterior abdominal wall

Serous pleural effusion or contiguous spread from ALA

Rupture from ALA into pleural space

Hepato-bronchial fistula with necrotic material in sputum may mimic
blood – trophozoites can be present

CNS involvement – rare – hematogenous spread

Genital ulcer can occur – by contiguous spread or hematogenous
route

18. 
Adhesion


Surface adhesins


Gal/GalNAc Lectin
Lipophosphoglycan like molecules
Invasion


Neuraminidase

Phospholipase A1, A2, and L1

Metallocollagenase


ATPase
Cysteine protease
Lysis

Amoebopore –
insertion of protein ion channels – cytolytic and bactericidal

19. 
E. dispar

E. moshkovskii

E. coli

E. hartmanii

E.gingivalis

E. dispar is morphologically
indistinguishable from E. histolytica and
so is E. moshkovskii

etc.
Most asymptomatic cases of amoebic
infestation are believed to be one of
these two species

The other species are also nonpathogenic but can be microscopically
differentiated

20. E. histolytica
E.coli
20-30 μm
20-50 μm
Active, unidirectional,
“purposeful motility”
Sluggish, nonpurposeful
Ectoplasm & endoplasm
Not defined
Cytoplasmic Inclusions
RBC, leukocytes, tissue debris,
no bacteria
Bacteria and cell debris but no
RBCs
Nucleus
Central karyosome, delicate
membrane, fine chromatin
grains
Eccentric nucleus, coarse
granules line a tough
membrane
Precyst
Oval, 10-20 μm, blunt
pseudopodium
20 μm, resembles E. histolytica
precyst
Spherical, 10-15 μm
Spherical, 15-20 μm
1-4
1-8
Rounded
Filamentous
Trophozoite
Size
Motility
Cytoplasm
Cyst
Size
No. of nuclei
Chromidial bars

21. 
Endolimax nana

Iodamoeba buetschlii

Commensals of the human gut

Can be easily differentiated microscopically

22. Samples :
Stool ( 3 consecutive samples)
Biopsy material from the ulcers (colonoscopy or
sigmoidoscopy)
Aspirate from liver abcess
Serum
Pleural fluid
Pericardial fluid
Sputum

23. 
Both saline and iodine wet mounts are prepared

Any motile trophozoite is better seen in saline mount

Iodine mount stains the internal structures and is used to
identify cysts

Permanent stains can also be used to stain smears

24. 
Antibody

Antigen detection
detection

ELISA

ELISA

Coagglutination

IHA

IFA
 Copro-antigen detection by ELISA is another
recent and very useful method

25. 
Xenic media

Locke-egg media ( NIH media – Locke’s
modification of Boeck and Drbohlav media)


Axenic media


Robinson’s media
Diamond media – TYI-S-33, YI-S, LYI-S-2
Monoxenic media

26. 
Locke’s solution ( per litre)
*
8 gm NaCl
0.2 gm CaCl2
*
0.01gm MgCl2
2 gm NaH2PO4
*
0.4 gm NaHCO3
0.3 gm KH2PO4

Break surface-sterilised eggs in a sterile container, blend and filter

To 45 ml of egg soln. add 12∙5 ml of Locke’s soln.

5-10 ml of this soln. is dispensed per tube and is solidified by
inspissation

Tubes are kept at an angle during solidification to form a slant

The media is then overlayed with 6-10 ml of Locke’s soln. and stored

Before inoculation, 0∙2 ml (1mg) of a stock soln. of rice starch
(5mg/ml) is added to each tube

27. 
Polymerase Chain Reaction

DNA probes

18 S rRNA gene sequencing for speciation

A zymodeme comprises those Entamoeba strains that share
the same electrophoretic pattern and mobility for certain
enzymes like – malic enzyme, phosphoglucomutase,
hexokinase, glucose phosphate isomerase, aldolase etc

24 different zymodemes – 21 of human strains

Currently however only 3 zymodemes are attributed to EH
one only for E. dispar

28. Luminal amoebicide
Diloxanide furoate
 Paromomycin
 Diiodohydroxiquin

Liver, gut wall and other tissues
Emetine
 Dehydroemetine

Hepatic amoebicide

Chloroquine
Both tissue and intestinal amoebicide (Nitroimidazoles)
Metronidazole [500-800 mg TDS X 5 (5-10) days]
 Tinidazole [ 2 gm OD X 1-3 days]
 Ornidazole [ 2 gm OD X 1-3 days]
